From: Dan Nelson
Date: March 10 2010 5:04pm
Subject: Re: mysql & RAID
List-Archive: http://lists.mysql.com/mysql/220899
Message-Id: <20100310170413.GM12122@dan.emsphone.com>
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In the last episode (Mar 10), John G. Heim said:
> I have read (and have been told) to stay away from RAID-5 for
> update-intensive systems. Are there performance concerns with RAID-10 as
> well? We will be buying from Dell (done deal for reasons too complicated
> to go into) and the disks they're selling are 146 Gb. I can get up to 8
> of them in the server we're buying. I asked them about just getting 2 big
> disks and going with RAID-1.
>
> My understanding is that with RAID-10, the system can do multiple reads and
> writes simultaneously so throughput is improved oversystems w/o RAID or with
> RAID-1. But the same logic would apply to RAID-5 only it doesn't work out
> that way.
RAID-5 has an extra penalty on small random writes due to the I/O required
to maintain the parity blocks (it does 2 reads and 2 writes for every write
your app does). RAID-10 is just a mirror so it doesn't have to worry about
that.
--
Dan Nelson
dnelson@stripped